Marine navigation is a process of piloting a vessel to a destination in a safe and expeditious manner. While sophisticated electronic equipment is available to aid in the navigation of larger vessels, the majority of mariners continue to navigate by using external reference marks.
A mark is any conspicuous object, natural or man-made, which has utility in establishing the position of a vessel or otherwise acting as a navigational aid. To be an effective navigational aid, each mark must be specifically identified and its position accurately known. Buoys, both lighted and unlighted, lighthouses and lightships are artificial marks designed and erected specifically to function as aids to navigation.
Buoys are the most numerous of all artificial aids to navigation. Buoys can function as daymarks based upon their shape, color and number. Some buoys, particularly those identifying turning points and channels, underwater obstructions, or mooring, docking or slip facilities, are provided with lights to facilitate night time navigation. Buoys may also incorporate horns or radio transmitters as navigational signals.
Signal buoys require an internal power source to operate the lighting system. Batteries are typically utilized as the power source for buoys on the basis of cost and maintenance considerations. Batteries are typically hardwired into the signal circuitry of the buoy so that the signal source is continually draining energy from the battery.
Mooring, docking or slip facilities likewise require some type of signal source to facilitate nighttime use. The location of the facility or other factors may make it impractical to run a power line for continuous nighttime energization of the signal source. In addition, continuously operated signal sources used with mooring, docking or slip facilities may have a negative impact on navigation inasmuch as these facilities may not be marked on navigational charts, thereby providing a source of confusion for mariners. Therefore, as a practical matter steady-state signal sources used with mooring, docking or slip facilities are typically battery powered and manually activated for nighttime operation.
EPIRBs are emergency signaling devices located on vessels and/or life vests/preservers which are typically activated in the event of an emergency such as a sinking vessel or man overboard. Since boat-mounted EPIRBs are designed for emergency use, these EPIRBs are typically powered by batteries. For EPIRBs incorporated in flotation devices, design constraints mandate the use of small compact batteries for the power source. Typically, the EPIRB is activated upon the occurrence of a maritime mishap such as a sinking vessel or man overboard.
Battery systems, however, are inherently limited in that the constant power drain upon the battery causes it to become depleted in a short time. A depleted battery cannot effectively function as a power source, and therefore batteries for buoys or docking facilities must be replaced at periodic intervals. Not only is such periodic replacement time consuming, but a navigational hazard exists when any buoy remains unpowered for any length of time. Alternatively, an expensive solar recharging system or cabling must be used to maintain adequate power.
For EPIRBs activated upon occurrence of a maritime mishap, a delay in rescue operations due to unfavorable weather conditions, unknown position of the mishap, or other adverse conditions can result in depletion of the battery power source prior to the arrival of the rescue craft. An inoperable EPIRB can adversely affect the rescue operation by delayinq or precluding the localization of the EPIRB, with concomitant dire consequences for the personnel awaiting rescue.